Processes for making activated carbon



Patented Sept. 11, 195i PROCESSES FOR MAKING ACTIVATED CARBON ErnstBer], deceased, late of Pittsburgh, Pa., by Walter George Berl,executor, Pittsburgh, Pa.

No Drawing. Original application September 23,

1942, Serial Nc.459,438. Divided and this application April 27, 1948,Serial No. 23,615

' 14 Claims. (01. ze a-444) This invention relates to processes of manu:facturing activated carbon, particularly briquetted activated carbon,and is a division oi appliation S rial 1 IQ..45. .4,3. S p ember 23 ideanow Patent No. 2,441,125, May 11, 19%8.

While activated carbon is useful for manypurposes, e. g. for thedechlori-nation of over-chlorinated water and for decolorization ofsugar solutions, there is a great demand for it at the pres-. ent timefor the adsorption of vapors and gases, especially poisonous gases thatmay be used in chemical warfare and poisonous or solvent vapors thatescape during industrial operations. For these purposes carbon in hardlumps of different particle sizes are desirable, if not necessary,Carbon produced from nut shells or hard wood can be manufactured withthe preferred particle size and hardness. However, activated carbon inpowdered form is produced in large quantities, either as a by-product ofthe processes of making the granular activated carbon or by specialprocesses such as disclosed in United States Patents No. 1,812,316 andNo. 1,851,888, Ernst Ber].

I de to lfidfil ll er d carboni as adsorption and for dechlorination ofwater and decolorization or other purposes, it may be desirable that theactive carbon be formed into dense lumps of special shapes and sizes bya briquetting process and without reducing the adsorption capacity ofthe carbon per unit of weight, In replacing the light powder by densepieces of desired geometric form, one gets increased adsorption capacityper unit of volume. The spe-. cial geometric form, e. g. saddles,cylinders,- etc, allows a lowering of pressure drop within the spacefilled with this formed activated carbon. This is of great importancefor mouthpieces of gas masks and for industrial uses, e. g. recovery ofsolvent vapors.

When used for adsorbing solvent vapors ;i nci-.-. dent to industrialoperations such as the manufacture of rayon, smokeless powder, recoveryof gasoline from natural gas, artificial leather, etc. these briquettedcarbons are subjected to higher temperature, often above the boilingpoint of water, for example during steaming of material that containsadsorbed vapors or by drying the Wet steamed carbon with hot air.Therefore, for this briquetting process it is necessary to use asbinders substances which will not. melt .or de-. compose at or belowsuch high temperature. The best way to carry out such a briquettingprocess is to use a binding material which in it? self has activeproperties; in other words, active carbon may play the role Of such acementing material. In addition to these requirements for a satisfactorybinder, other difficulties have been encountered in briquetting. alreadyactivated hydrophobic carbon. I

I many case sma l q nt t 0f b n rs 9 not bind the particles of thisstrongly hydrophobic material together strongly enough. Gas films on theactivated carbonparticles may be the reason for this behavior. v Whencertain briquetted activated carbons are submitted to differenttemperatures, they are converted into fine powder. In other cases, thebinder used subtant all re uces he a tivity i the t r a This is due tothe fact that decomposition products of the binder, for instance pitcherstarch, at higher temperatures form non-active, graphitic carbon whichcontainslittle bound hydrogen and oxygen. This so-c alled"secondary'carbon covers the active places of the real active carbon anddeleteriouslyaffects its activity.

Furthermore, the great demand for activated carbon requires that newand'additional sources of raw materials be found to provide an adequatesupply of activated carbon of desired qualities and at reasonable cost;and this in turn necessitates new or improved methods of treating theraw materials during this conversion process in order to get activatedcarbons which show a max.- imum adsorption capacity towards vapors,poison gases, dye stuffs and which react quickly and ef-, ficiently withthose conversion compounds of halogens which are formed by the reactionof halogens with chlorinated water, e. g. hypo? chlorous acid.

Therefore, prime objects of this invention are to provide a novel andimproved method of producing activated carbon, whereby numerous car.-bonaceous raw materials may be utilized to make a powdered activated,partly hydrophobic inter-.1 mediate product; and to provide a new andimproved method for forming said intermediate product at low cost intolumps of desired shape and particle size that will be retained after theconversion of this intermediate product into highly activated carbonswhich fulfill the requirements for gas adsorption, water dechlorinationor decolorization operations, etc.

o h b c o h s i vention i to pro i a novel and improved method ofbriquetting intermediate products and powdered activated carbonincluding the utilization of new and especially effective bind rs,whereby the adsorption properties of the carbon shall not be deleeteriously aifected and briquets or lumps shall be capable ofwithstanding high temperatures, ressu an WI W hou .difiesmfiwotherobjects, d an ages iidre ii f t e ine t n ill ear m he ipllowin deeerition.

:It has been found that these objectscan be attained by a process whichin general consistsvin utilizing such carbonaceous raw materials aswater-soluble acid sludges from oil refineries, dense wood, lignite,waste sulphiteliquor, etc,

. 3 treating them with activating agents, for example potassium salts,pre-coalifying the resultant potassium salts of sulfonic and carboxylicacids and of phenols, and grinding the resulting material to open thelarge holes formedby gas during the first coalification process carriedout between 300 and 600 G. Then for briquetting the powder the processproceeds by adding a finely powdered binder, such as a phenolformaldehyde resin, heating the mixture at temperatures of from 130 to250 C. under high pressure, e. g. 500 to 10,000 p. s. i., therebypolymerizing the resin; during or before this polymerization operationshaping the mixture into lumps or particles of the desired form, e. g.,small rods, saddles, plates, disks, cylinders, balls, etc., and thenheating the formed material to temperatures between 800 C. and 1200 C.

More particularly describing the invention, it may be pointed out thatduring the pre-activation of different raw materials at temperaturesbetween 300 and 500 C. the materialitself goes often through a plasticstage. During this plastic stage a simultaneous development of gascomposed of carbon dioxide, water and organic compounds-methane andhomologues, etc.-takes place. More or less porous material results afterthe development of gases and vapors has reached an end. Itisadvantageous to heat the material which has to be activated in thepresence or in the absence of activating agents to temperatures whichare above those temperatures where the plastic stage exists and tomaintain these temperatures until the development of cracking gases hasceased. Cooling of the material results in a more or less foamy mass oflight weight. This mass which is brittle at room temperature is thenpulverized. The larger holes which are responsible for the very lightweight are opened and a brownish powder with higher apparent densityresults.

This preheated material produced from potassium compounds of sulfonicand carboxylic acids and of phenols which are present at the start orformed during the pre-activation already contains activating substances,for instance potassium sulfate, potassium sulfite, potassium carbonate,potassium sulfide, potassium cyanide, etc., or those activatingsubstances may be added afterwards.

Potassium sulfate and potassium sulfite act at temperatures above 500 C.as oxidizing and corroding materials. They are converted at temperaturesabove 700 C. in absence of oxygen mostly into potassium sulfide.Potassium sulfate and potassium sulflte produce from the resultingintermediate products activated carbons with lower apparent density andsomewhat larger capillaries so that vapors of substances with highermolecular weight, for instance chloropicrin, can enter thesecapillaries. The yield in activated carbon is lower, the adsorption ofdyestufls is increased, also the reactivity towards hypochlorous acid,H001 and similar derivatives of bromine and iodine.

Potassium sulfide is also an activating substance. A potassiumactivation of the intermedi ate product obtained between 300-600 C. atthe activation temperature between-800 and 1200 C. takes place as is thecase with potassium sulfate. There is no oxidizing action by boundoxygen. Therefore, yields in activated carbon are increased, finercapillaries are produced so that vapors of higher molecular substances.cannot enter very easily into these fine capillaries andbe retained. Theapparent density of the resulting activated carbons is somewhat higherthan those which are produced in the presence of larger amounts ofpotassium sulfate. The decolorizing poweris not as high as with thepotassium-sulfate activated carbon.

By controlling the amount of the added potassium salt and its oxygencontent in the mixture which has to be submitted to 800-l200 C., i. e.,by changing the relationship between the organic material in theprecoalified product to the potas sium ,content and the oxygen contentof these potassium compounds, it is possible to obtain different carbonsin powder form or in form of larger, harder lumps with differentapparent densities, different yields and different adsorption anddecolorization power.

If briquetted material has to be produced, the binder is added to theintermediate product obtained at temperatures between 300 C. and 600 C.either with or after the addition of potassium salts. For this bindersuch material should be used which at high temperature decomposes anditself forms through reaction with the potassium salts present activatedcarbon which cements together the activated carbon produced from theground mass. Very hard and dense particles of any desired geometricshape can be obtained in this way. It has been found that phenolformaldehyde-resins, urea formaldehyde resins, resins with the basis ofmelamine, and similar resins are best suited for this purpose.

It is important that the material which has been partly degasifiedpreviously at moderate temperatures (BOO-600 C.) in order to get moredense material afterwards, should contain a certain amount of boundoxygen; in other words, it should have certain hydrophilic qualities.Under those conditions it is necessary to use only rather small amounts,5-30%, of the right kind of binding resinto obtain the desired results.

Completely activated carbons with very little bound oxygen and hydrogen,due to the gas films formed on their surface and to their hydrophobicqualities, need more binder than the partly hydrophilic intermediateproduct produced at 300- 600 C. One has to add also potassium compoundsto this mixture of hydrophobic activated carbon and binder so that thefollowing activation at elevated temperature (8001200 C.) producesactivated, cementing carbon from the binder material itself. Thepreheated, partly hydrophilic, finely powdered, practically non-activematerial and, if necessary, another amount of activatin substances,preferably potassium compounds, are mixed intimately with the finelypowdered binder, for instance phenol formaldehyde resin. The resultingfinely pulverized and thoroughly mixed material is formed into anygeometric shape while it is submitted to higher temperature underpressure; this in order to avoid the formation of larger holes caused bythe formation of steam and decomposition products produced from thepolymerization reaction of the added resin. If submitted to higherpressure (500-10,000 p. s. i.) at temperatures between and 250 C.,preferably at about 180 C., the artificial resin is transformedinto theso-called B' and C stage. Then this polymerized synthetic resin cementstogether perfectly the particles of the precoalified material plus theactivating substances, for instance potassium compounds.

The resulting, very hard and dense material is then subjected to highertemperatures between 800 and 1200 C., preferably to about 950 C. inabsence of free oxygen. This can be done at normal, reduced or increasedpressure. Then an activation process takes place without great change ofthe structure and the dimensions of the previously briquetted material.Inorganic, oxygen-containin material, for instance potassium sulfate orpotassium sulfite, is reduced to potassium sulfide. This newly producedand formerly added potassium sulfide also acts as potassium-saltactivator. It forms potassiumgraphitic compounds CBK and 018K whichdecompose with water. They are responsible for part of the activationreaction. Sulfur present corrodes the surface of the newly produced,small crystallites by the formation of carbon disulfide, carbonoxysulfide and other volatile products. The organic material isconverted into excellent dense, briquetted active carbon. Afterextraction with water of the potassium sulfide produced, hard structureswith the necessary high apparent density are obtained, which prove to beexcellent gas mask dechlorinating and decolorizing carbons.

It has been found that a mixture of organic material coalifled at about400 C., potassium compounds and synthetic resins, especially phenolformaldehyde resins, as binder ive excellent results with a minimum ofused resin. The resin itself in the presence of potassium compoundscontributes to the activation process. About 50% of the weight of thedry resin is converted into an activated carbon which cements togetherthe activated carbon particles resulting from the activation of theorganic material.

The specific steps of the process may be varied as will be apparent fromthe following examples:

EXAMPLE 1 Water-soluble acid sludge from the oil refineries 400-450 C.There results a rather light powder which contains, besides'organicsubstances; smaller amounts of water-insoluble potassium compounds boundchemically with the organic material and larger amounts ofwater-soluble, free potassium salts, mostly potassium sulfate. Thispowder can be used as such for further operations. If necessary ordesired one may'extract'all or some of the potassium sulfate or add moreof it. With or Without the extraction of part or all of the potassiumsulfate, potassium sulfide (K2S) or other potassium compounds free of orpoor in bound oxygen, e. g. potassium cyanide, potassium sulfocyanide,potassium cyanate, may be added. The organic substances which are formedby the coalification between 300 and 600 C. contain enough hydrophiloxygen-containing groups so that the resulting material wets rathereasily with water and does not adsorb much gas. The activity of thisbrown organic residue is very low.

This material must be ground to very fine particle size in order to openthe larger holes which have been formed by the development of gasesthrough-the previous heating. Then to this mixture finely powderedorganic resins, for instance phenol formaldehyde resins are added.According to the fineness of the powder and its nature, 5-30%,preferably 712%, of phenol formaldehyde resins are used. The phenolformaldehyde resins may be utilized also in dissolved form.

This mixture of organic material plus potassium compounds with boundsulfur and phenol resin is then converted into the B and C resin stageby a treatment under pressure (1000-10,000 p. s. i.) at temperaturesbetween 130 and- 250 C., preferably at about 180 C. Through the p01-ymerization of the phenol resin a perfect cementing of the organicmaterial and potassium salts takes place. During or before thispolymerization operation under pressure, the mixture can be convertedinto the desired geometric form, for instance into disks, plates, rods,cylinders, saddles; balls, etc.

The now resulting material must be submitted to activation temperaturesbetween 800'and 1200" C., preferably between 900 and 1000 C. Then manyreactions take place. At this high temperature a rearrangement of carbonatoms under formation of a graphite lattice occurs. The potassiumcompounds act as activating substances. They corrode the graphite-likematerial. Free, unsaturated valences are formed, as are also finer andcoarser capillaries, in this new resulting material which is poor inbound oxygen and hydrogen. During this activation process the phenolformaldehyde resin in the presence of the. potassium compounds is alsoconverted into graphitic but active carbon which cements the,

carbon particles together.

Without change in the external structure of acid sludge is compared withgas mask carbon.

made from cocoanut shell as follows:

The fol-= 'It'can be seen from these results that the activatedgas-adsorbing carbon on a volume and Weight basis is superior to gascarbons made from cocoanut shells which until now have been consideredthe best available material.

EXAMPLE 2 Instead of using phenol formaldehyde resins as described inExample 1, urea formaldehyde resins are used. Similar results areobtained.

EXAMPLE 3 Instead of using phenol formaldehyde resins as used in Example1, or urea formaldehyde resins as used in Example 2, resin with thebasis of melamine present similar results.

EXAMPLE 4 Potassium salts of water-soluble acid sludge are mixedaccording to U. S. Patent 1,851,888 with wood chips, dense, wood, orlignites, or bituminous coals. This intimate mixture to which, ifnecessary, potassium sulfate or potassium sulfite, or potassium sulfidemay be added, is heated to temperatures of about 300-600 0., preferablybetween 400 and 450 C., in order to carry out the first step of acoalification'process during which large amounts of coalification gasesare formed. After having carried out the decomposition process at thismoderate temperature, the material is ground up to very fine particlesize, for instance less than 200 mesh. The material may be used as it isor further amounts of potassium sulfate, or potassium sulfide, ormixtures of potassium sulfate and potassium sulfide, may be added. It ispermissible to extract some of the watersoluble potassium compounds richin oxygen, and optionally other potassium compounds free of or poor inoxygen, for instance K28, KCN, KCNS, KCNO, may be added. To this veryintimate mixture, resins as described in Examples 1, 2 and 3 are addedin suflicient quantity, either in solid or in dissolved form. Themixture of coalified material, potassium salts and resin binder is thensubjected to higher temperature (BO-250 C.) and pressure (BOO-10,000 p.s. i.) and the formation of appropriate geometric forms may be carriedout. This material should be subjected, preferably in the absence ofoxygen, to temperatures between 800 and 1200 0., best between 900 and1000 C. The activation process which is a corrosion process takes place.After the activation process has been carried out and the material hasbeen cooled, the resulting K28 is extracted with water. It may be usedfor the neutralization of another batch of water-soluble acid sludge.The then resulting hydrogen sulfide may be converted into sulfur, orsulfuric acid, or oleum.

The resulting activated carbon may be extracted, if necessary ordesired, with diluted hydrochloric acid in order to remove ironcompounds and to decompose strongly adsorbed potassium sulfide orpotassium polysulfide and may be washed with diluted ammonia. It may bereheated, if necessary or desired, to temperatures up to 500-700 C., thesecond heating removing sulfur which is formed from the decomposition ofpolysulfides. This sulfur otherwise occupies part of the active placesof the gas carbon. The adsorbed sulfur can be removed also by anysolvent for it, for instance warm benzene, dichlorbenzene, or waterysodium sul= fite solutions.

The removal of the adsorbed sulfur by heating or the activated carbon toabout 500-700 C; or

by the extraction with organic or inorganic solvents increases theadsorption capacity towards vapors and dissolved dyestufi moleculesabout 5-20%.

The resulting activated carbon gives results similar to those describedin Table I, Example 1.

EXAMPLE 5 Dense wood or lignite is mixed with potassium sulfate solutionso that the dry mixture contains between 15 and 60% of potassium sulfateor potassium sulfide. This mixture is brought to temperatures up to 550C., preferably between 400 and 450 C. The resulting coalified mass ispulverized so that large holes caused by the development of gas duringthe plastic stage are opened. This material then is mixed withartificial resins described in Examples 1, 2 and 3. Briquetting andheating processes are the same as described in Examples 1 and 4. Theresulting potassium sulfide after the formation of activated carbon hastaken place at high temperature, has to be removed by a systematicextraction with Water. The activated carbon after having been briquettedor not may be submitted to a second heating process or extractionprocess as described in Example 4.

EXAMPLE 6 To waste sulfite liquor resulting from the production ofsulfite pulp, potassium carbonate as a fine-powder or in watery solutionis added until the whole amount of calcium salts of lignin sulfonicacids is converted into water-soluble potassium compounds. The resultingsolution of these potassium compounds is separated by sedimentation orfiltration from the precipitated calcium carbonate. One may add to thissolution potassium sulfate or potassium sulfide in i order to change theactivity of the finally resulting activated carbon. The neutral oralkaline liquid is then dried.

As hereinbefore stated, the qualities of the activated carbon can beregulated or varied by varying the ratio of potassium to organicsubstance and by controlling the ratio of oxygen bound on the potassiumcompounds to the organic substance. Most of the potassium is chemicallybound in this mixture as potassium salt of lignin sulfonic acids. Ifdesired, potassium sulphate or potassium sulphite, substances with arelatively large amount of bound oxygen, may be added to the drymaterial, or sulfide, cyanide or sulfocyanide of potassium having nobound oxygen may be added.

Using more potassium sulfate reduces the final yield in active carbon,decreases the apparent density which may go down to .06 and increasesthe adsorption capacity toward larger gas molecules and larger moleculeslike dyestufl molecules dissolved in liquids. Increasing the amount ofpotassium sulfide increases the yield and apparent density, decreasessomewhat the adsorption capacity toward larger gas molecules withoutinfluencing the adsorption capacity for smaller gas molecules, anddecreases somewhat the adsorption capacity towards larger molecules, forinstance dyestuif molecules, dissolved in liquids.

The coalification steps come next. The dry material is subjected totemperatures between 300 and 600 0., best between 400 and 500 C.

11 to organic substance in the product formed by the first heating stepthe apparent density of the final product is lowered.

3. The steps in the process of making activated carbon, comprisingheating a mixture of a potassium salt or a water-soluble tar acid fromthe production of oil products and of a carbonaceous material to BOO-600C., afterwards intimately mixing the thus formed product with acontrolled amount of a water-soluble potassium compound being a memberof the group consisting of potassium carbonate, potassium sulfate,

potassium sulfite, potassium sulfide, potassium cyanide, potassiumsulfocyanide and potassium cyanate, and with a resin binder, forming theintimate mixture into the desired geometric form, heating'it to atemperature of from 110 C. to 250 C. at a pressure from aboutsilo-10,000

p. s. i., activating the resulting product at a temperature from 800 tol200 (3., and extracting said last-named water-soluble potassiumcompound; whereby by increasing the ratio of chemically bound potassiumto organic substance in the product formed by the first heating step,fine capillaries are produced in the final product, and by increasingthe ratio of chemically bound oxygen to organic substance in the productformed by the first heating step the apparent density of the finalproduct is lowered.

4. The steps ina process of making activated carbon, comprising heatinga mixture of a potassium salt of a water-soluble tar acid from theproduction of oil products and carbonaceous material to 300-600 C.,intimately mixing the thus formed product with a resin binder, formingsaid intimate mixture into the desired geometric form, polymerizing saidresin, activating the resulting product at a temperature from about 800C. to about 1200" C. in contact with potassium sulfide intimatelyintermingled with said product. and extracting residual potassiumsulfide; whereby by increasing the ratio of chemically bound potassiumto organic substance in the product formed by the first heating step,fine capillaries are produced in the final product.

5. The steps in a process of making activated carbon, comprising heatinga potassium salt of a water-soluble tar acid from the production of oilproducts to a temperature between 300-600 0., afterwards intimatelymixing the thus formed product with a controlled amount of awatersoluble potassium compound being a member of the group consistingof potassium carbonate, potassium sulfate, potassium sulfite, potassiumsulfide, potassium cyanide, potassium sulfocyanide and potassiumcyanate, activating said intimate mixture at temperatures from 800 to1200 C., and extracting said last-named water-soluble potassiumcompound; whereby by increasing the ratio of chemically bound potassiumto organic substance in the product formed by the first heating step,fine capillaries are produced in the final product, and by increasingthe ratio of chemically bound oxygen to organic substance in the productformed by the first heating step the apparent density of the finalproduct is lowered.

6. The steps in a process of making activated carbon, comprising heatinga potassium salt of a water-soluble tar acid from the production of oilproducts to a temperature between 300-600 0., afterwards intimatelymixing the thus formed product with a controlled amount of water-solublepotassium compound being a member of the group consisting of potassiumcarbonate, potassium sulfate, potassium sulfite, potassium sulfide,

' pota'ssiu'm cyanide, potassium sulfocyanide, and

potassium cyanate, activating said intimate mixtu'reat temperatures from800 to 1200 C., and extracting said last-named water-soluble potassiumcompound and removing adsorbed sulfur; whereby by increasing the ratioof chemically bound potassium to organic substance in the product formedby the first heating step, fine capillaries are produced in the finalproduct, and by increas ng the ratio of chemically bound oxygen toorganic substance in the product formed by the first heating step theapparent density of the final product is lowered.

'7. The steps in a process of making activated carbon, comprisingheating a potassium salt of a water-soluble tar acid from the productionor oil products to a temperature between 300-600 C., afterwardsintimately mixing the thus formed product with a water-soluble potassiumcompound being a member of the group consisting of potassium carbonate,potassium sulfate, potassium sulfite, potassium sulfide, potassiumcyanide, potassium sulfocyanide and potassium cyanate, and with a resinbinder, forming the intimate mixture into the desired geometric form,heating it to a temperature of from C. to 250 C. at a pressure fromabout 500-10,000 p. s. i., activating the resulting product at atemperature from 800 to 1200" C., and extracting said last-namedwater-soluble potassium compound; whereby by increasing the ratio ofchemically bound potassium to organic substance in the product formed bythe first heating step, fine capillaries are produced in the finalproduct, and by increasing the ratio or chemically bound oxygen toorganic substance in the product formed by the first heating step, theapparent density of the final product is lowered.

8. The steps in a process of making activated carbon, comprising heatinga potassium salt of a water-soluble tar acid from the production of oilproducts to BOO-600 0., intimately m xing the thus formed product with athermosetting resin binder, forming said intimate mixture into thedesired geometric form, polymerizing said resin, heating the resultingproduct at a temperature from about 800 C., to about 1200" C., incontact with potassium sulfide intimately intermingled with the product,and extracting residual potassium sulfide; whereby by increasing theratio of chemically bound potassium to organic substance in the productformed by the first heating step, fine capillaries are produced in thefinal product.

9. The steps in the process of making activated carbon, comprisingheating a mixture of car bonaceous material and of a controlled amountof a water-soluble potassium compound being a member of the groupconsisting of potassium carbonate, potassium sulfate, potassium sulfite,potassium sulfide, potassium cyanide, potassium sulfocyanide andpotassium cyanate to 300-600 C., activating said intimate mixture attemperatures from 800 to 1200 0., and extracting said lastnamedwater-soluble potassium compound; whereby by increasing the ratio ofchemically bound potassium to organic substance in the product formed bythe first heating step, fine capillaries are produced in the finalproduct, and by increasing the ratio of chemically bound oxygen toorganic substance in the product formed by the first heating step, theapparent density of the final product is lowered.

10. The steps in the process of making activated, carbon, comprisingheating a mixture of carbonaceous material thus formed and of acontrolled amount of a water-soluble potassium compound being a memberof the group consisting of potassium carbonate, potassium sulfate,potassium sulfite, potassium sulfide, potassium cyanide, potassiumsulfocyanide and potassium cyanate to 300-600 C., activating saidintimate mixture at temperatures from 800 to 1200 C. and extracting saidlast-named water-soluble potassium compound, and removing adsorbedsulfur; whereby by increasing the ratio of chemically bound potassium toorganic substance in the product formed by the first heating step, finecapillaries are produced in the final product, and by increasing theratio of chemically bound oxygen to organic substance in the productformed by the first heating step, the apparent density Of the finalproduct is lowered.

11. The steps in the process of making activated carbon, comprisingheating a mixture of carbonaceous material and of a controlled amount ofa water-soluble potassium compound being a member of the groupconsisting of potassium carbonate, potassium sulfate, potassium sulfitc,potassium sulfide, potassium cyanide, potassium sulfocyanide andpotassium cyanate to BOO-600 C., intimately mixing the product thusformed with a thermosetting resin binder, forming the intimate mixtureinto the desired geometric form, heating it to a temperature of from 110C. to 250 C. at a pressure from about 500-10,000 p. s. i., activatingthe resulting product at a temperature from 800 to 1200 C., andextracting said lastnamed Water-soluble potassium compound; whereby byincreasing the ratio of chemically bound potassium to organic substancein the product formed by the first heating step, fine capillaries areproduced in the final product, and by increasing the ratio of chemicallybound oxygen to organic substance in the product formed by the firstheating step, the apparent density of the final product is lowered.

12. The steps in a process of making activated carbon, comprisingheating a mixture of carbonaceous material and potassium sulfide to 300-600 C., intimately mixing the product thus formed with a thermosettingresin binder, forming said intimate mixture into the desired geometricform, polymerizing said resin, activating the resulting product at atemperature from about 800 C. to about 1200 C. in contact with potassiumsulfide intimately intermingled with said product, and extractingresidual potassium sulfide; whereby by increasing the ratio ofchemically bound potassium to organic substance in the product formed bythe first heating step, fine capillaries are produced in the finalproduct.

13. The steps in the process of making activated carbon, comprisingadding to carbonaceous material a water-soluble potassium sulfurcompound, heating the mixture to between 400-550 0., pulverizing thethus formed product, intimately mixing the pulverized product with athermosetting resin binder, forming the intimate mixture into thedesired geometric form, and heating it to a temperature from 130 to 250C. at a pressure from about 500-10,000 p. s. i.,

' activating the resulting product at temperatures WALTER GEORGE BERL,Executor of the Estate of Ernst Berl, Deceased.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,968,846 Morrell Aug. '7, 19341,989,107 Morrell Jan. 29, 1935 2,008,144 Morrell July 16, 19352,056,854 Hene Oct. 6, 1936 2,377,063 Adler May 29, 1945 2,441,125 BerlMay 11, 1948

1. THE STEPS IN THE PROCESS OF MAKING ACTIVATED CARBON, COMPRISINGHEATING A MIXTURE OF A POTASSIUM SALT OF A WATER-SOLUBLE TAR ACID FROMTHE PRODUCTION OF OIL PRODUCTS AND OF A CARBONACEOUS MATERIAL TO300-600* C., AFTERWARDS INTIMATELY MIXING THE THUS FORMED PRODUCT WITH ACONTROLLED AMOUNT OF A WATER-SOLUBLE POTASSIUM COMPOUND BEING A MEMBEROF THE GROUP CONSISTING OF POTASSIUM CARBONATE, POTASSIUM SULFATE,POTASSIUM SULFITE, POTASSIUM SULFIDE, POTASSIUM CYANIDE, POTASSIUMSULFOCYANIDE, AND POTASSIUM CYANTE, ACTIVATING SAID INTIMATE MIXTURE ATTEMPERATURES FROM 800 TO 1200* C., AND EXTRACTING SAID LAST-NAMEDWATER-SOLUBLE POTASSIUM COMPOUND; WHEREBY BY INCREASING THE RATION OFCHEMICALLY BOUND POTASSIUM TO ORGANIC SUBSTANCE IN THE PRODUCT, FINECAPILLARIES ARE PRODUCED IN THE FINAL PRODUCT, AND BY INCREASING THERATIO OF CHEMICALLY BOUND OXYGEN TO ORGANIC SUBSTANCE IN THE PRODUCTFORMED BY THE FIRST HEATING STEP THE APPARENT DENSITY OF THE FINALPRODUCT IS LOWERED.